Configuration of beamforming settings for a wireless radio transceiver device

ABSTRACT

There is provided mechanisms for configuring beamforming settings. A method is performed by a wireless radio transceiver device configured to communicate in directional beams. The method comprises obtaining a performance indication requiring configuration of the beamforming settings of the wireless radio transceiver device. The method comprises selecting a similarity measure objective based on what kind of performance indication was obtained. The method comprises determining, based on the similarity measure objective and results from a similarity measure procedure applied to pairs of received signals, an order in which to evaluate the directional beams when configuring the beamforming settings.

TECHNICAL FIELD

Embodiments presented herein relate to a method, a wireless radiotransceiver device, a computer program, and a computer program productfor configuring beamforming settings.

BACKGROUND

In communications networks, there may be a challenge to obtain goodperformance and capacity for a given communications protocol, itsparameters and the physical environment in which the communicationsnetwork is deployed.

For example, for future generations of mobile communications systemsfrequency bands at many different carrier frequencies could be needed.For example, low such frequency bands could be needed to achievesufficient network coverage for wireless radio transceiver devices andhigher frequency bands (e.g. at millimeter wavelengths (mmW), i.e. nearand above 30 GHz) could be needed to reach required network capacity. Ingeneral terms, at high frequencies the propagation properties of theradio channel are more challenging and beamforming both at the accessnode of the network and at the wireless radio transceiver devices mightbe required to reach a sufficient link budget.

The wireless radio transceiver devices could implement beamforming bymeans of analog beamforming, digital beamforming, or hybrid beamforming.Each implementation has its advantages and disadvantages. A digitalbeamforming implementation is the most flexible implementation of thethree but also the costliest due to the large number of required radiochains and baseband chains. An analog beamforming implementation is theleast flexible but cheaper to manufacture due to a reduced number ofradio chains and baseband chains compared to the digital beamformingimplementation. A hybrid beamforming implementation is a compromisebetween the analog and the digital beamforming implementations. As theskilled person understands, depending on cost and performancerequirements of different wireless radio transceiver devices, differentimplementations will be needed.

When the wireless radio transceiver devices uses analog beamforming itcould be challenging for the wireless radio transceiver devices todetermine if a currently used beam produced by using the analogbeamforming is a good beam in terms of a given signal quality criterionor if there exist other beams that if generated by the analogbeamforming would perform significantly better in terms of the givensignal quality criterion. In order to evaluate if any other such beam isbetter a beam finding procedures, for example using beam referencesignals (BRS), could be used. However, performing such a proceduretypically requires comparatively much overhead signaling between theaccess node and the wireless radio transceiver device which, thus, willtemporarily occupy radio resources and increase the average interferencein the network.

Hence, there is a need for an improved beam finding procedure.

SUMMARY

An object of embodiments herein is to enable efficient beam finding fora wireless radio transceiver device.

According to a first aspect there is presented a method for configuringbeamforming settings. The method is performed by a wireless radiotransceiver device configured to communicate in directional beams. Themethod comprises obtaining a performance indication requiringconfiguration of the beamforming settings of the wireless radiotransceiver device. The method comprises selecting a similarity measureobjective based on what kind of performance indication was obtained. Themethod comprises determining, based on the similarity measure objectiveand results from a similarity measure procedure applied to pairs ofreceived signals, an order in which to evaluate the directional beamswhen configuring the beamforming settings.

Advantageously this provides efficient configuring of beamformingsettings for the wireless radio transceiver device.

Advantageously this enables the wireless radio transceiver device toefficiently select which (combinations of) directional beams to be usedwhen configuring the beamforming settings, thus resulting in a fast andefficient beam training procedure

According to a second aspect there is presented a wireless radiotransceiver device for configuring beamforming settings. The wirelessradio transceiver device is configured to communicate in directionalbeams. The wireless radio transceiver device comprises processingcircuitry. The processing circuitry is configured to cause wirelessradio transceiver device to obtain a performance indication requiringconfiguration of the beamforming settings of the wireless radiotransceiver device. The processing circuitry is configured to causewireless radio transceiver device to select a similarity measureobjective based on what kind of performance indication was obtained. Theprocessing circuitry is configured to cause wireless radio transceiverdevice to determine, based on the similarity measure objective andresults from a similarity measure procedure applied to pairs of receivedsignals, an order in which to evaluate the directional beams whenconfiguring the beamforming settings.

According to a third aspect there is presented a wireless radiotransceiver device for configuring beamforming settings. The wirelessradio transceiver device is configured to communicate in directionalbeams. The wireless radio transceiver device comprises processingcircuitry and a storage medium. The storage medium stores instructionsthat, when executed by the processing circuitry, cause the wirelessradio transceiver device to perform operations, or steps. Theoperations, or steps, cause the wireless radio transceiver device toobtain a performance indication requiring configuration of thebeamforming settings of the wireless radio transceiver device. Theoperations, or steps, cause the wireless radio transceiver device toselect a similarity measure objective based on what kind of performanceindication was obtained. The operations, or steps, cause the wirelessradio transceiver device to determine, based on the similarity measureobjective and results from a similarity measure procedure applied topairs of received signals, an order in which to evaluate the directionalbeams when configuring the beamforming settings.

According to a fourth aspect there is presented a wireless radiotransceiver device for configuring beamforming settings. The wirelessradio transceiver device is configured to communicate in directionalbeams. The wireless radio transceiver device comprises an obtain moduleconfigured to obtain a performance indication requiring configuration ofthe beamforming settings of the wireless radio transceiver device. Thewireless radio transceiver device comprises a select module configuredto select a similarity measure objective based on what kind ofperformance indication was obtained. The wireless radio transceiverdevice comprises a determine module configured to determine, based onthe similarity measure objective and results from a similarity measureprocedure applied to pairs of received signals, an order in which toevaluate the directional beams when configuring the beamformingsettings.

According to a fifth aspect there is presented a computer program forconfiguring beamforming settings, the computer program comprisingcomputer program code which, when run on a wireless radio transceiverdevice configured to communicate in directional beams, causes thewireless radio transceiver device to perform a method according to thefirst aspect.

According to a sixth aspect there is presented a computer programproduct comprising a computer program according to the fifth aspect anda computer readable storage medium on which the computer program isstored. The computer readable storage medium could be a non-transitorycomputer readable storage medium.

It is to be noted that any feature of the first, second, third, fourth,fifth and sixth aspects may be applied to any other aspect, whereverappropriate. Likewise, any advantage of the first aspect may equallyapply to the second, third, fourth, fifth and/or sixth aspect,respectively, and vice versa. Other objectives, features and advantagesof the enclosed embodiments will be apparent from the following detaileddisclosure, from the attached dependent claims as well as from thedrawings.

Generally, all terms used in the claims are to be interpreted accordingto their ordinary meaning in the technical field, unless explicitlydefined otherwise herein. All references to “a/an/the element,apparatus, component, means, step, etc.” are to be interpreted openly asreferring to at least one instance of the element, apparatus, component,means, step, etc., unless explicitly stated otherwise. The steps of anymethod disclosed herein do not have to be performed in the exact orderdisclosed, unless explicitly stated.

BRIEF DESCRIPTION OF THE DRAWINGS

The inventive concept is now described, by way of example, withreference to the accompanying drawings, in which:

FIG. 1 is a schematic diagram illustrating a communications networkaccording to embodiments;

FIG. 2 schematically illustrates a wireless radio transceiver deviceaccording to an embodiment;

FIGS. 3, 4, and 5 are flowcharts of methods according to embodiments;

FIG. 6 is a schematic diagram showing functional units of a wirelessradio transceiver device according to an embodiment;

FIG. 7 is a schematic diagram showing functional modules of a wirelessradio transceiver device according to an embodiment;

FIG. 8 schematically illustrates an access node according to anembodiment;

FIG. 9 schematically illustrates a wireless device according to anembodiment; and

FIG. 10 shows one example of a computer program product comprisingcomputer readable storage medium according to an embodiment.

DETAILED DESCRIPTION

The inventive concept will now be described more fully hereinafter withreference to the accompanying drawings, in which certain embodiments ofthe inventive concept are shown. This inventive concept may, however, beembodied in many different forms and should not be construed as limitedto the embodiments set forth herein; rather, these embodiments areprovided by way of example so that this disclosure will be thorough andcomplete, and will fully convey the scope of the inventive concept tothose skilled in the art. Like numbers refer to like elements throughoutthe description. Any step or feature illustrated by dashed lines shouldbe regarded as optional.

FIG. 1 is a schematic diagram illustrating a communications network 100comprising an access node 300 providing network access to a wirelessradio transceiver device 200. The wireless radio transceiver device 200is assumed to comprise at least two receiver chains and is configured toreceive signals from the access node 300 in directional beams 110 a, 110b, 120 a, 120 b. The wireless radio transceiver device 200 is thusconfigured to communicate in directional beams 110 a, 110 b, 120 a, 120b (in contrast to omnidirectional beams).

The access node 300 could be any of a radio access network node, radiobase station, base transceiver station, node B, evolved node B, g nodeB, or access point. The wireless radio transceiver device 200 could beany of a wireless device, mobile station, mobile phone, handset,wireless local loop phone, user equipment (UE), smartphone, laptopcomputer, tablet computer, or wireless sensor.

FIG. 2 illustrates the wireless radio transceiver device 200 accordingto an embodiment. The wireless radio transceiver device 200 is equippedwith two receiver chains 130 a, 130 b, each comprising its own basebandprocessing (BPP) chain 140 a, 140 b. Each baseband processing chain 140a, 140 b is operatively connected to its own analog beamformer 150 a,150 b. Each analog beamformer 150 a, 150 b has its own set of analogprecoder weights (e.g. defined by a codebook) by means of which thedifferent directional beams 110 a, 110 b, 120 a, 120 b can be formed.For illustrative purposes it is assumed that receiver chain 130 a isconfigured to receive transmissions from the access node 300 selectivelyin either directional beam 110 a or directional beam 110 b and thatreceiver chain 130 b is configured to receive transmissions from theaccess node 300 selectively in either directional beam 120 a ordirectional beam 120 b. Hence, in the illustrative example of FIG. 2,each of the analog beamformers 150 a, 150 b switches between two analogprecoders; AP1 for generating directional beams 110 a, 120 a and AP2 forgenerating directional beams 110 b, 120 b. Antennas at the wirelessradio transceiver device 200 might be implemented in an irregularfashion and the physical structure of the wireless radio transceiverdevice 200 might affect the radiation patterns of the antennas, whichmeans that the same analog precoder applied to two different analogbeamformers 150 a, 150 b might create totally different radiationpatterns, which is illustrated schematically in FIG. 2, where thedirectional beams 110 a and 120 a are pointing in mutually differentdirections and where the directional beams 110 b and 120 b are pointingin mutually different directions (assuming that the same analog precoderAP1 is applied at both analog beamformers 150 a, 150 b to generatedirectional beams 110 a and 120 a, and the same analog precoder AP2 isapplied at both analog beamformers 150 a, 150 b to generate directionalbeams 110 b and 120 b).

The embodiments disclosed herein relate to mechanisms for configuringbeamforming settings, i.e., which of the directional beams 110 a, 110 b,120 a, 120 b to use for transmission to, and reception from, the accessnode 300. In order to obtain such mechanisms there is provided awireless radio transceiver device 200, a method performed by thewireless radio transceiver device 200, a computer program productcomprising code, for example in the form of a computer program, thatwhen run on a wireless radio transceiver device 200, causes the wirelessradio transceiver device 200 to perform the method.

FIGS. 3 and 4 are flow charts illustrating embodiments of methods forconfiguring beamforming settings. The methods are performed by thewireless radio transceiver device 200. The methods are advantageouslyprovided as computer programs 1020.

Reference is now made to FIG. 3 illustrating a method for configuringbeamforming settings as performed by the wireless radio transceiverdevice 200 according to an embodiment. As disclosed above, the wirelessradio transceiver device 200 is configured to communicate in directionalbeams 110 a, 110 b, 120 a, 120 b.

S102: The wireless radio transceiver device 200 obtains a performanceindication requiring configuration of the beamforming settings of thewireless radio transceiver device 200. Examples of performanceindications will be disclosed below.

By gathering statistics of received signals during for example activemode and/or dormant mode for the wireless radio transceiver device 200,a similarity measure can be determined between the analog precoders AP1,AP2 applied to the different analog beamformers 150 a, 150 b. Whichsimilarity measure to use depends on the type of performance indicationobtained in step S102. Hence, the wireless radio transceiver device 200is configured to step S104:

S104: The wireless radio transceiver device 200 selects a similaritymeasure objective based on what kind of performance indication wasobtained.

A result of a similarity measure procedure being applied to pairs ofreceived signals is then used by the wireless radio transceiver device200 to determine the order in which the directional beams 110 a, 110 b,120 a, 120 b are to be evaluated when configuring the beamformingsettings. Hence, the wireless radio transceiver device 200 is configuredto step S106:

S106: The wireless radio transceiver device 200 determines, based on thesimilarity measure objective and results from a similarity measureprocedure applied to pairs of received signals, an order in which toevaluate the directional beams 110 a, 110 b, 120 a, 120 b whenconfiguring the beamforming settings. Examples of how the similaritymeasure objective and the results from the similarity measure procedurecan be used to determine the order will be disclosed below.

In this respect not all directional beams 110 a, 110 b, 120 a, 120 bneed to be evaluated when configuring the beamforming settings.

Referring back to the illustrative example of FIG. 2, the directionalbeam 110 b (i.e., when using precoder AP2 for the upper beamformer 150a) is pointing in (substantially) the same direction as the directionalbeam 120 a (i.e., when using AP1 for the lower beamformer 150 b). Hence,for example, when collecting statistics of measured received signalstrength values during long time periods the signal strength similarityresulting from applying the similarity measure procedure to the pair ofsignals received using directional beam 110 b and directional beam 120 awill be comparatively high. Assume further that the wireless radiotransceiver device 200 is about to lose coverage and that a beam findingprocedure therefore is initiated by the access node 300. In this case,it would thus be advantageous for the wireless radio transceiver device200 to initially in the beam finding procedure not use a combination ofbeamformers 150 a, 150 b and precoders AP1, AP2 where AP2 is applied onthe upper beamformer 150 a and AP1 is applied on the lower beamformer150 b since this combination is likely to result in high signal strengthsimilarity. In fact, it might be enough for the wireless radiotransceiver device 200 to test either AP2 applied for the upperbeamformer 150 a or either AP1 applied for the lower beamformer 150 b,but not both, because if AP2 applied for the upper beamformer 150 a doesnot yield an acceptable received signal strength, most certainly neitherAP1 applied for the lower beamformer 150 b will yield an acceptablereceived signal strength. Instead, in this case, it could be moreadvantageous for the wireless radio transceiver device 200 to evaluateprecoders with low signal strength similarity in order to as quickly aspossible find a suitable directional beam, or combination of directionalbeams.

There may be different examples of received signals for the similaritymeasure procedure to be applied to. In general terms, the receivedsignals could be either reference signals (such as channel stateinformation reference signals (CSI-RS) or synchronization signals) ordata signals. The received signals could thus be any signals received bythe wireless radio transceiver device 200 from the access node 300 andhence no special reference signals dedicated particularly for thesimilarity measure procedure are needed.

Embodiments relating to further details of configuring beamformingsettings as performed by the wireless radio transceiver device 200 willnow be disclosed.

Reference is now made to FIG. 4 illustrating methods for configuringbeamforming settings as performed by the wireless radio transceiverdevice 200 according to further embodiments. It is assumed that stepsS102, S104, S106 are performed as described above with reference to FIG.3 and a thus repeated description thereof is therefore omitted

Once the wireless radio transceiver device 20 has determined the orderin which to evaluate the directional beams 110 a, 110 b, 120 a, 120 bwhen the beamforming settings are configured the wireless radiotransceiver device 200 could perform the evaluation. Hence, according toan embodiment the wireless radio transceiver device 200 is configured toperform step S108:

S108: The wireless radio transceiver device 200 evaluates thedirectional beams 110 a, 110 b, 120 a, 120 b according to the determinedorder (i.e., the order determined in step S106).

It is here to be understood that respective precoders AP1, AP2 need tobe used in order to evaluate directional beams 110 a, 110 b, 120 a, 120b. Hence, in this respect, evaluating the directional beams 110 a, 110b, 120 a, 120 b is equivalent to evaluating the precoders AP1, AP2 perbeamformer 150 a, 150 b.

There could be different ways for the wireless radio transceiver device200 to change beamforming settings. According to some aspects, signalprocessing resources available in the radio transceiver device 200 arere-allocated during the evaluation of the directional beams 110 a, 110b, 120 a, 120 b in step S108. Hence, according to an embodiment theradio transceiver device 200 a comprises signal processing resources,and is configured to perform the evaluation of the directional beams 110a, 110 b, 120 a, 120 b by performing step S108 a:

S108 a: The radio transceiver device 200 a re-maps the signal processingto resources from one beam port to another beam port according to thedetermined order in which the directional beams 110 a, 110 b, 1200 a,120 b are to be evaluated.

There may be different pairs of received signals to which the similaritymeasure procedure is applied.

In some aspects the similarity measure procedure is applied to pairs ofsignals received using mutually different beamformers 150 a, 150 b.Hence, according to an embodiment the radio transceiver device 200comprises at least two receiver chains 130 a, 130 b, and the pairs ofsignals are received from mutually different ones of the at least tworeceiver chains 130 a, 130 b. Thereby correlation can be determinedbetween signals from different beamformers 150 a, 150 b but sameprecoder AP1, AP2.

In some aspects the similarity measure procedure is applied to pairs ofsignals received using the same beamformer 150 a, 150 b. Hence,according to an embodiment the radio transceiver device 200 comprises atleast one receiver chain 130 a, 130 b, and the pairs of signals arereceived from the same receiver chain 130 a, 130 b. Thereby, correlationcan be determined between signals from the same beamformer 150 a, 150 bbut different precoders AP1, AP2.

Further, the similarity measure procedure could be applied both to pairsof signals received using mutually different beamformers 150 a, 150 band to pairs of signals received using the same beamformer 150 a, 150 b.As will be further disclosed below it could thus be preferred todetermine a similarity measure both between analog precoders AP1, AP2applied to different analog beamformers 150 a, 150 b and between analogprecoders AP1, AP2 applied to the same analog beamformer 150 a, 150 b.

There could be different ways for the radio transceiver device 200 todetermine whether to use pairs of signals received from same receiverchain 130 a, 130 b. In some aspects, signals received by the same analogbeamformer 150 a, 150 b are only considered if the signals are receivedwithin the coherence time of the radio propagation channel in which thesignals are received. Hence, according to an embodiment the signals arereceived on a radio channel having a coherence time, and signals of eachpair of signals (that are received from the same receiver chain 130 a,130 b) are received within the coherence time.

There could be different ways for the radio transceiver device 200 todetermine the similarity measure of a pair of signals received from thesame receiver chain 130 a, 130 b. In some aspects the similarity measurebetween precoders AP1, AP2 of the same analog beamformer 150 a, 150 b isfound by comparing the similarity measure with precoders AP1, AP2 ofanother beamformer 150 a, 150 b. Hence, according to an embodiment theradio transceiver device 200 comprises at least two receiver chains 130a, 130 b, and the similarity measure of a pair of signals received fromsame ones of the at least two receiver chains 130 a, 130 b is based onthe similarity measure between each of the signals in the pair ofsignals with the same signal from another one of the at least tworeceiver chains 130 a, 130 b. This embodiment may be applicable forsimilarity measures based on signal strength but not on complex-valuedsimilarity measures.

There may be different examples of similarity measures. According to anembodiment the similarity measure procedure determines correlationbetween the pairs of received signals.

As indicated above, the similarity measure could be related to signalstrength similarity. In general terms, the similarity measure couldeither be related to signal strength similarity (considering onlyamplitude/envelope of the received signals) or complex-valued similarity(considering both phase and amplitude/envelope of the received signals).That is, according to a first embodiment the similarity measureprocedure is evaluated in terms of signal strength similarity betweenthe pairs of received signals. That is, according to a second embodimentthe similarity measure procedure is evaluated in terms of complex-valuedsimilarity between the pairs of received signals.

There may be different examples of similarity measure objectives to beselected in step S104. A first similarity measure objective is that theresult of the similarity measure procedure being applied to pairs ofreceived signals should be as high as possible. According to anembodiment the similarity measure objective is to evaluate thedirectional beams 110 a, 110 b, 120 a, 120 b according descendingsimilarity measure results. That is, the order determined in step S106orders the directional beams 110 a, 110 b, 120 a, 120 b from highest tolowest measure results. Using this similarity measure objective thedirectional beams 10 a, 110 b, 120 a, 120 b could then be evaluated instep S108 according descending similarity measure results.

A second similarity measure objective is that the result of thesimilarity measure procedure being applied to pairs of received signalsshould be as low as possible. According to an embodiment the similaritymeasure objective is to evaluate the directional beams 110 a, 110 b, 120a, 120 b according ascending similarity measure results. That is, theorder determined in step S106 orders the directional beams 110 a, 110 b,1200 a, 120 b from lowest to highest similarity measure results. Usingthis similarity measure objective the directional beams 110 a, 110 b,120 a, 120 b could then be evaluated in step S108 according ascendingsimilarity measure results. For example, once the first two directionalbeams having the lowest similarity measure result have been tested, thenext directional beam to be tested could be that of the remainingdirectional beams that has the lowest similarity measure result to thealready tested directional beams, and so on.

There may be different performance indications for the wireless radiotransceiver device 200 to obtain in step S102.

According to an embodiment the performance indication pertains tonetwork coverage of the wireless radio transceiver device 200. Thesimilarity measure objective could then be to span as large angularspace as possible when evaluating the directional beams 110 a, 110 b,120 a, 120 b. Hence, the order in step S106 is then determined such thatas much as possible of the angular space is spanned using as fewdirectional beams 110 a, 110 b, 120 a, 120 b as possible. Further, thesimilarity measure procedure can be evaluated in terms of signalstrength similarity of the received signals. That is, the similaritymeasure procedure could be determined in terms of signal strengthsimilarity when the performance indication pertains to network coverageand the similarity measure objective is to span as large angular spaceas possible.

According to an embodiment the performance indication pertains tobitrate of the wireless radio transceiver device 200. The similaritymeasure objective could then be to use as high rank as possible whenevaluating the directional beams 110 a, 110 b, 120 a, 120 b. Hence, theorder in step S106 is then determined such that as high rank as possiblecould be used using as few directional beams 110 a, 110 b, 120 a, 120 bas possible.

That is, according to a first embodiment the similarity measureprocedure is evaluated in terms of signal strength similarity of thereceived signals and the similarity measure objective is be to evaluatethe directional beams 110 a, 110 b, 120 a, 120 b according descendingsimilarity measure results when the performance indication pertains tobitrate and when the similarity measure objective is to use as high rankas possible. One example of determining signal strength similarity is toevaluate the correlation of the total received signal strength over acertain bandwidth.

Further, according to a second embodiment the similarity measureprocedure is evaluated in terms of complex-valued similarity of thereceived signals and the similarity measure objective is to evaluate thedirectional beams 110 a, 110 b, 120 a, 120 b according ascendingsimilarity measure results when the performance indication pertains tobitrate and when the similarity measure objective is to use as high rankas possible.

If the similarity measure objective is to use as high rank as possible,the pairs of directional beams should have as high as possible signalstrength similarity and as low as possible complex-valued similarity.That is, if the similarity measure objective is to use as high rank aspossible, the directional beams 110 a, 110 b, 120 a, 120 b could beevaluated according to a joint function of descending signal strengthsimilarity and ascending complex-valued to similarity.

As disclosed above, it could be preferred to determine a similaritymeasure both between analog precoders AP1, AP2 applied to differentanalog beamformers 150 a, 150 b and between analog precoders AP1, AP2applied to the same analog beamformer 150 a, 150 b. This implies that itcould be advantageous to measure the correlation of received signals forall different combination of analog beamformers 150 a, 150 b and analogprecoders AP1, AP2. One reason for this is that two or more analogprecoders AP1, AP2 applied to the same analog beamformer 150 a, 150 bmight result in a large correlation of the received signals, and henceit might be enough to only use one of these highly correlated analogbeamformers 150 a, 150 b during a beamfinding procedure. Estimatingcorrelation between signals received using different precoders AP1, AP2of different analog beamformers 150 a, 150 b could be accomplished bymeasuring, for example, signal strength at each respective receiverchain 130 a, 130 b simultaneously during normal operation of thewireless radio transceiver device 200.

In general terms, only one analog precoder AP1, AP2 can be used at atime for each analog beamformer 150 a, 150 b, and when the wirelessradio transceiver device 200 changes analog precoder AP1, AP2 the radiopropagation channel (excluding antenna patterns) might change as well.Therefore, it could be preferred to consider the coherence time of theradio propagation channel when determining the correlation betweensignals received using different analog precoders AP1, AP2 of the sameanalog beamformer 150 a, 150 b. For correlation of received signalstrength, however, the correlation between analog precoders AP1, AP2 ofthe same analog beamformer 150 a, 150 b could be found also by comparingthe correlation with analog precoders AP1, AP2 of another analogbeamformer 150 a, 150 b. For example, assume that AP1 and AP2 for analogbeamformer 150 b has high correlation with AP2 of the analog beamformer150 a, then AP1 and AP2 of the analog beamformer 150 b can be assumed tohave strong correlation as well.

That is, in case the performance indication pertains to increasing thenetwork coverage, preferably directional beams 110 a, 110 b, 120 a, 120b with low signal strength correlation between them should be used firstto span the angular space as quickly as possible. If the signal strengthcorrelation is very high between two different combinations of analogprecoders AP1, AP2 and analog beamformers 150 a, 150 b, it might beenough to use only one of the combinations during the beam findingprocedure.

Further, in case the performance indication pertains to increasing thebitrate (due to low rank in the channel), it could be preferred toprioritize evaluation of analog precoders AP1, AP2 that have lowcomplex-valued correlation whilst still having a strong signal strengthcorrelation in order to facilitate spatial multiplexing.

FIG. 5 is a flowchart of a particular embodiment for configuringbeamforming settings, the method being performed by a wireless radiotransceiver device 200 according to at least some of the above disclosedembodiments.

S201: The wireless radio transceiver device 200 gathers statistics ofreceived signals during active mode and/or dormant mode for differentcombinations of analog precoders AP1, AP2 and analog beamformers 150 a,150 b.

S202: The wireless radio transceiver device 200 uses the gatherstatistics to determine a similarity measure value (such as signalstrength correlation or complex-valued correlation) of the receivedsignals between the different combinations of analog precoders AP1, AP2and analog beamformers 150 a, 150 b.

S203: The wireless radio transceiver device 200 uses the similaritymeasure value to determine which combinations of analog precoders AP1,AP2 and analog beamformers 150 a, 150 b that should be included in abeam training procedure and in which order the combinations of analogprecoders AP1, AP2 and analog beamformers 150 a, 150 b should be used ina beam finding procedure.

FIG. 6 schematically illustrates, in terms of a number of functionalunits, the components of a wireless radio transceiver device 200according to an embodiment. Processing circuitry 210 is provided usingany combination of one or more of a suitable central processing unit(CPU), multiprocessor, microcontroller, digital signal processor (DSP),etc., capable of executing software instructions stored in a computerprogram product 1010 (as in FIG. 10), e.g. in the form of a storagemedium 230. The processing circuitry 210 may further be provided as atleast one application specific integrated circuit (ASIC), or fieldprogrammable gate array (FPGA).

Particularly, the processing circuitry 210 is configured to cause thewireless radio transceiver device 200 to perform a set of operations, orsteps, S102-S108 a, S201-S203, as disclosed above. For example, thestorage medium 230 may store the set of operations, and the processingcircuitry 210 may be configured to retrieve the set of operations fromthe storage medium 230 to cause the wireless radio transceiver device200 to perform the set of operations. The set of operations may beprovided as a set of executable instructions.

Thus the processing circuitry 210 is thereby arranged to execute methodsas herein disclosed. The storage medium 230 may also comprise persistentstorage, which, for example, can be any single one or combination ofmagnetic memory, optical memory, solid state memory or even remotelymounted memory. The wireless radio transceiver device 200 may furthercomprise a communications interface 220 at least configured forcommunications with the access node 300. As such the communicationsinterface 220 may comprise one or more transmitters and receivers,comprising analogue and digital components. The processing circuitry 210controls the general operation of the wireless radio transceiver device200 e.g. by sending data and control signals to the communicationsinterface 220 and the storage medium 230, by receiving data and reportsfrom the communications interface 220, and by retrieving data andinstructions from the storage medium 230. Other components, as well asthe related functionality, of the wireless radio transceiver device 200are omitted in order not to obscure the concepts presented herein.

FIG. 7 schematically illustrates, in terms of a number of functionalmodules, the components of a wireless radio transceiver device 200according to an embodiment. The wireless radio transceiver device 200 ofFIG. 7 comprises a number of functional modules; a determine module 210a configured to perform step S102, a select module 210 b configured toperform step S104, and a determine module 210 c configured to performstep S106. The wireless radio transceiver device 200 of FIG. 7 mayfurther comprise a number of optional functional modules, such as any ofan evaluate module 210 d configured to perform step S108, and a re-mapmodule 210 e configured to perform step S108 a.

In general terms, each functional module 210 a-210 e may in oneembodiment be implemented only in hardware and in another embodimentwith the help of software, i.e., the latter embodiment having computerprogram instructions stored on the storage medium 230 which when run onthe processing circuitry makes the wireless radio transceiver device 200perform the corresponding steps mentioned above in conjunction with FIG.7. It should also be mentioned that even though the modules correspondto parts of a computer program, they do not need to be separate modulestherein, but the way in which they are implemented in software isdependent on the programming language used. Preferably, one or more orall functional modules 210 a-210 e may be implemented by the processingcircuitry 210, possibly in cooperation with the communications interface220 and/or the storage medium 230. The processing circuitry 210 may thusbe configured to from the storage medium 230 fetch instructions asprovided by a functional module 210 a-210 e and to execute theseinstructions, thereby performing any steps as disclosed herein.

The radio transceiver device 200 may be provided as a standalone deviceor as a part of at least one further device. For example, the radiotransceiver device 200 may be implemented in, part of, or co-locatedwith, an access node 800 (as in FIG. 8) or a wireless device 900 (as inFIG. 9). Hence, according to some aspects there is provided an accessnode 800 and/or wireless device 900 comprising a radio transceiverdevice 200 as herein disclosed.

Further, a first portion of the instructions performed by the radiotransceiver device 200 may be executed in a first device, and a secondportion of the of the instructions performed by the radio transceiverdevice 200 may be executed in a second device; the herein disclosedembodiments are not limited to any particular number of devices on whichthe instructions performed by the radio transceiver device 200 may beexecuted. Hence, the methods according to the herein disclosedembodiments are suitable to be performed by a radio transceiver device200 residing in a cloud computational environment. Therefore, although asingle processing circuitry 210 is illustrated in FIG. 6 the processingcircuitry 210 may be distributed among a plurality of devices, or nodes.The same applies to the functional modules 210 a-210 e of FIG. 7 and thecomputer program 1020 of FIG. 10 (see below).

FIG. 10 shows one example of a computer program product 1010 comprisingcomputer readable storage medium 1030. On this computer readable storagemedium 1030, a computer program 1020 can be stored, which computerprogram 1020 can cause the processing circuitry 210 and theretooperatively coupled entities and devices, such as the communicationsinterface 220 and the storage medium 230, to execute methods accordingto embodiments described herein. The computer program 1020 and/orcomputer program product 1010 may thus provide means for performing anysteps as herein disclosed.

In the example of FIG. 10, the computer program product o11 isillustrated as an optical disc, such as a CD (compact disc) or a DVD(digital versatile disc) or a Blu-Ray disc. The computer program product1010 could also be embodied as a memory, such as a random access memory(RAM), a read-only memory (ROM), an erasable programmable read-onlymemory (EPROM), or an electrically erasable programmable read-onlymemory (EEPROM) and more particularly as a non-volatile storage mediumof a device in an external memory such as a USB (Universal Serial Bus)memory or a Flash memory, such as a compact Flash memory. Thus, whilethe computer program 1020 is here schematically shown as a track on thedepicted optical disk, the computer program 1020 can be stored in anyway which is suitable for the computer program product 1010.

The inventive concept has mainly been described above with reference toa few embodiments. However, as is readily appreciated by a personskilled in the art, other embodiments than the ones disclosed above areequally possible within the scope of the inventive concept, as definedby the appended patent claims.

1. A method of evaluating directional beams, the method being performedby a wireless radio transceiver device, the method comprising: receivinga first signal using a first directional beam; receiving a second signalusing a second directional beam; determining a correlation between thereceived first signal and the received second signal; and based at leaston the determined correlation, determining an order of evaluatingdirectional beams including the first directional beam and/or the seconddirectional beam.
 2. The method of claim 1, wherein the correlationbetween the received first signal and the received second signalcorresponds to a similarity between at least one characteristic of thereceived first signal and at least one characteristic of the receivedsecond signal.
 3. The method of claim 2, wherein the similarity betweensaid at least one characteristic of the received first signal and saidat least one characteristic of the received second signal is (i) signalstrength similarity between the received first signal and the receivedsecond signal or (ii) complex-valued similarity between the receivedfirst signal and the received second signal.
 4. The method of claim 1,wherein the wireless radio transceiver device comprises signalprocessing resources, and evaluating the directional beams comprisesre-mapping the signal processing resources from one beam port to anotherbeam port according to the determined order.
 5. The method of claim 1,wherein the wireless radio transceiver device comprises a first receiverchain and a second receiver chain, the first directional beam isassociated with the first receiver chain, and the second directionalbeam is associated with the second receiver chain.
 6. The method ofclaim 1, wherein the wireless radio transceiver device comprises atleast one receiver chain, the first directional beam is associated withsaid at least one receiver chain, and the second directional beam isassociated with said at least one receiver chain.
 7. The method of claim6, wherein the first signal and the second signal are received within acoherence time of a radio channel.
 8. The method of claim 1, wherein thewireless radio transceiver device comprises at least two receiverchains, and a similarity measure of a pair of signals received from sameones of the at least two receiver chains is based on a similaritymeasure between each of the signals in the pair of signals with the samesignal from another one of the at least two receiver chains.
 9. Themethod of claim 1, further comprising: obtaining a performanceindication requiring configuration of beamforming settings of thewireless radio transceiver device; and selecting a similarity measureobjective based on the type of the obtained performance indication,wherein the order of evaluating the directional beams is determinedfurther based on the selected similarity measure objective.
 10. Themethod of claim 9, wherein the similarity measure objective is toevaluate the directional beams according to (i) descending similaritymeasure results or (ii) ascending similarity measure results.
 11. Themethod of claim 9, wherein the performance indication pertains to (i)network coverage of the wireless radio transceiver device or (ii)bitrate of the wireless radio transceiver device.
 12. The method ofclaim 9, wherein the similarity measure objective is (i) to span aslarge an angular space as possible when evaluating the directional beamsor (ii) to use as high a rank as possible when evaluating thedirectional beams.
 13. The method of claim 9, wherein the correlationbetween the received first signal and the received second signalcorresponds to signal strength similarity of the received first signaland the received second signal when (i) the performance indicationpertains to network coverage and (ii) the similarity measure objectiveis to span as large an angular space as possible.
 14. The method ofclaim 9, wherein the correlation between the received first signal andthe received second signal corresponds to signal strength similarity ofthe received first signal and the received second signal, and thesimilarity measure objective is to evaluate the directional beamsaccording to descending similarity measure results when the performanceindication pertains to bitrate and when the similarity measure objectiveis to use as high a rank as possible.
 15. The method of claim 9, whereinthe correlation between the received first signal and the receivedsecond signal corresponds to complex-valued similarity of the receivedfirst signal and the received second signal, and the similarity measureobjective is to evaluate the directional beams according ascendingsimilarity measure results when the performance indication pertains tobitrate and when the similarity measure objective is to use as high arank as possible.
 16. A wireless radio transceiver device, the wirelessradio transceiver device comprising: processing circuitry; acommunication interface comprising a receiver, wherein the communicationinterface is configured to receive a first signal using a firstdirectional beam and a second signal using a second directional beam;and a storage medium storing instructions that, when executed by theprocessing circuitry, cause the wireless radio transceiver device to:determine a correlation between the received first signal and thereceived second signal; and based at least on the determinedcorrelation, determine an order of evaluating directional beamsincluding the first directional beam and/or the second directional beam.17. The wireless radio transceiver device of claim 16, wherein theinstructions, when executed by the processing circuitry, further causethe wireless radio transceiver device to: obtain a performanceindication requiring configuration of beamforming settings of thewireless radio transceiver device; and select a similarity measureobjective based on the type of the obtained performance indication,wherein the order of evaluating the directional beams is determinedfurther based on the selected similarity measure objective.
 18. Acomputer program product comprising a non-transitory computer readablestorage medium storing a computer program, the computer programcomprising computer code which, when run on processing circuitry of awireless radio transceiver device, causes the wireless radio transceiverdevice to: determine a correlation between a first signal received atthe wireless radio transceiver device using a first directional beam anda second signal received at the wireless radio transceiver device usinga second directional beam; and based at least on the determinedcorrelation, determine an order of evaluating directional beamsincluding the first directional beam and/or the second directional beam.19. The computer program product of claim 18, wherein the computer code,when run on the processing circuitry of the wireless radio transceiverdevice, further causes the wireless radio transceiver device to: obtaina performance indication requiring configuration of beamforming settingsof the wireless radio transceiver device; and select a similaritymeasure objective based on the type of the obtained performanceindication, wherein the order of evaluating the directional beams isdetermined further based on the selected similarity measure objective.